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Live Tube map shows the power of TfL's data

Blimey. Just six days after London's transport co-ordinator, Tfl, announced that it was throwing the gates wide open to developers wanting access to its vast treasure troves of data, and we've already got a web-based mashup that plots the approximate position of every single underground train, updated every second or so.

The map uses Tfl's live departure board information to calculate the positions of the trains. It knows when a train is 7, 6, 5, 4, 3, 2 or 1 minute away, and when it arrives at a station, and can calculate its approximate position and speed accordingly. As any seasoned London traveller knows, those departure boards can sometimes bend the truth just a little, so expect the same inaccuracies from this map.

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In fact, watch for a few minutes, and you'll no doubt see some of the errors in the data feed -- trains travelling far faster than could be possible, or taking wild routes off the track, haring off below parks or housing estates as if they'd suddenly decided that they'd seen enough of the same old boring routes, and wanted to try something different.

Zooming in close to a busy station such as King's Cross or Hammersmith also reveals some of the difficulties faced by the Underground's controllers and drivers, with trains entering and leaving the station as often as every 5-10 seconds.

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Somerville said about the map: "Live departure data is fetched from the TfL API, and then it does a bit of maths and magic. It’s surprisingly okay given this was done in only a few hours and the many naming/location issues, some unresolved (a small number of stations are misplaced or missing; inter-station journey times need improvement; occasional trains behave oddly due to duplicate IDs)."